Method for treating metallic melts

ABSTRACT

Method and apparatus for treating a metallic melt, such as molten steel in a ladle, are disclosed. The apparatus includes an inner tubular member, through which an additive is delivered to within the melt, and a coaxially disposed outer tubular member, the annulus between the two tubular members serving as a passageway for gas delivered to the melt. The gas is introduced into the melt through a porous refractory element positioned about the ends of the tubular members.

United States Patent 1 Bernsmann Dec. 11, 1973 METHOD FOR TREATINGMETALLIC MELTS [75] Inventor: Gert P. Bernsmann, Pittsburgh, Pa.

[73] Assignee: Jones & Laughlin Steel Corporation,

Pittsburgh, Pa.

[22] Filed: Dec. 11, 1970 a 21 Appl. No.: 97,384

Related U.S. Application Data [62] Division of Ser. No. 802,518, Feb.26, 1969, Pat. No.

[52] U.S. Cl 75/58, 75/129, 75/130 [51] Int. Cl. C2lc 7/00, C22c 33/00[58] Field of Search 75/58, 129, 130, 75/130 R, 130 B [56] ReferencesCited UNITED STATES PATENTS 2,781,260 2/1957 Grandpierre 75/130 B3,642,466 2/1972 McCaulay 75/130 B 2,776,206 l/1957 Klingbeil 75/130 B2,871,008 l/1959 Spire 75/130 R 3,598,575 8/1971 .larysta 75/130 B1,562,655 11/1925 Pacz 75/58 2,085,802 7/1937 Hardy 75/58 2,698,749l/1955 Fishell 75/130 B X 3,251,680 5/1966 0055 et a1. 75/59 3,634,0751/1972 l-loff 75/135 3,666,449 5/1972 Alt 75/130 B FOREIGN PATENTS ORAPPLICATIONS 972,708 10/1964 Great Britain 75/130 13 PrimaryExaminer-Charles N. Lovell Assistant ExaminerPeter D. RosenbergAtl0rneyT. A. Zalenski [57] ABSTRACT Method and apparatus for treating ametallic melt, such as molten steel in a ladle, are disclosed. Theapparatus includes an inner tubular member, through which an additive isdelivered to within the melt, and a coaxially disposed outer tubularmember, the annulus between the two tubular members serving as apassageway for gas delivered to the melt. The gas is introduced into themelt through a porous refractory element positioned about the ends ofthe tubular members.

7 Claims, 2 Drawing Figures PATENTED BEE] I 1975 METHOD FOR TREATINGMETALLIC MELTS This is a division of Application Ser. No. 802,518, filedFeb. 26, l969, now US. Pat. No. 3,615,085.

This invention relates generally to method and apparatus for treating ametallic melt and, more particularly, to method and apparatus foreffecting an efficient and controlled deoxidation of molten steel.

Controlled and uniform deoxidation of molten steel in a ladle can berealized by simultaneously delivering to a spot deep within the meltthrough a lance submerged therein a deoxidant, such as aluminum, and anargon gas stream. Employing the apparatus of the present invention, thedeoxidant is maintained out of contact with the molten steel until itexits from the submerged lance whereupon it dissolves and reacts withthe oxygen in the steel. The argon gas stream is passed from the lanceto the deoxidant melt reaction zone through an inherently porousrefractory element or a refractory element made porous by the provisionof a plurality of fine passageways therein. The gas issuing from theporous element is in a finely subdivided state, thus promoting thestirring of dissolved, unreacted deoxidant throughout the melt andenhancing removal of deoxidation products to the melt surface. Thesubdivided gas particles also protect the porous element fromoverheating and early destruction from the reaction heat generated bythe deoxidant and liquid steel.

The present invention is also useful in making additions to molten steelof materials, such as lithium and magnesium, which react violently withthe molten steel or which possess high vapor pressures. By submergingthe lance within the melt, initial contact and reaction between theadditive and the molten steel is constrained to occur at any desireddepth, obviating the dangers of a violent surface reaction and thecomplete oxidation of the additive before it has penetrated the melt toany appreciable degree.

The present invention is also used to make alloy additions to moltensteel. Uniform distribution of an alloy throughout a melt is insured byits introduction deep within the melt and the dispersing action of thefinely subdivided gas stream.

Preferably, the additive is fed to the molten steel through the lance inthe form of a continuous rod so that a controlled feed rate is readilymaintained. This permits deoxidation of the melt to be closelycontrolled so that it can be accurately deoxidized to any desireddegree. For purposes of this disclosure, the term rod also includesshapes referred to variously as wire and bar. As-cast rods as well asrods formed by mechanical working are used. In addition, rods formed ofparticles of an additive or additives held together by a suitable binderare employed. Accordingly, a rod can be homogeneous and comprise asingle additive or be heterogeneous and comprise several additives.

An object of the invention is to provide method and apparatus forsimultaneously introducing an additive and finely divided gas stream tometallic melts. Another object of the invention is to provide method andapparatus for effecting controlled deoxidation of molten steel. Yetanother object of the invention is to pro vide for such controlleddeoxidation by simultaneously feeding a deoxidant, in the form of a rod,and argon to the molten steel in a ladle.

These and other objects and advantages of the invention will be moreapparent from the following detailed description thereof with referenceto the drawing in which:

FIG. 1 is a longitudinal view, partly in section, of a first embodimentof the invention; and

FIG. 2 is a longitudinal view, partly in section of a second embodimentof the invention.

Referring to FIG. 1, a lance embodying the principles of this inventionis shown and includes a steel inner tubular member 10 and steel outertubular member 11 concentric therewith. The annulus 20 between thetubular members is closed off at the top of member 11 by sealing means12, comprising packing gland l3 welded to member 11, packing box 14 andpacking 15.

A circular flange 16 is secured, as by welding, to the lower ends oftubular members 10 and 11, an opening 17 being provided in the center ofthe flange in line with the interior of member 10.

A porous head or stone 18 of refractory material, of the type known inthe art, is positioned about the lower ends of tubular members 10 and11. The porous head includes a centrally disposed cylindrical recess 19forming a shoulder 20 in the head. The porous head is supported onflange 16 by its shoulder 20, and is firmly secured thereto byrefractory cement 21.

To provide protection against the action of the molten metal, in whichthe lance in normal operation is submerged, a refractory sleeve 22consisting of a plurality of stacked cylindrical tiles. 23-23 isprovided about the tubular members 10 and 11, extending upwardly of saidmembers from the porous head. The bottommost tile rests on head 18 andthe stack is held in place by nut 24 which is threaded onto the exteriorof tubular member 11 so as to bear down on washer 25 placed on thetopmost tile. In addition, the joints between tiles are filled with arefractory cement.

A conduit 26 is tapped into outer tubular member 11 and is in fluidcommunication with annulus 29. In operation, conduit 26 is attached to agas source.

Ports 27-27 are provided in outer tubular member 11 in the vicinity ofporous head 18 to provide a passageway for gas to flow from annulus 29into and through said head. Also, ports 28-28 are provided in tubularmember 10 for establishing fluid communication between annulus 29 andthe interior of member 10, enabling a positive pressure to be applied tosaid interior, preventing the ingress therein of the fluid in which thelance submerged.

In employing the apparatus described deoxidize a molten steel bath, thelance is lowered deep within the bath, an aluminum rod is fed downwardlyfrom the top of inner tubular member 10, exiting from the bottom thereofthrough opening 17 and into the molten steel bath whereupon the aluminumreacts with the oxygen in the bath. Simultaneously, argon gas isdelivered through conduit 26 into annulus 29. The argon passes from theannulus through ports 27-27 and then through porous head 18 into themelt. The finely subdi-- vided gas emerging from head 18 dispersesthroughout the bath, promoting stirring of the dissolved unreactedaluminum throughout the bath and removal of deoxidation products to thebath surface. The argon also protects the stopper head from overheatingfrom the heat generated by the reacting aluminum and oxygen.

The argon gas flow rate is maintained at least high enough to establish,through ports 28-28, a pressure within tubular member 10 sufficient tobalance the pressure within the bath at the level of the bottom of head18. Entry of the molten metal into tubular member and the consequentreaction therein of oxygen and aluminum is thereby precluded.

The embodiment of the invention illustrated in FIG. 2, is similar to theembodient of FIG. 1, and the same reference numerals used in bothfigures refer to the same features in both. In addition to conduit 26,the embodiment of FIG. 2 has a second conduit 30, tapped into the wallof tubular member 10 and in fluid communication with the interiorthereof. Conduit 30 is connected to a gas source independent of thesource to which conduit 26 is connected and transports gas to theinterior of member 10 to establish a positive pressure therein at leastbalancing the pressure of the bath at the level where the porous head ispositioned.

The provision of a second conduit 30 and independent gas sourceassociated therewith to maintain a suitable back pressure within member10, enables the interior of the latter to be kept isolated from annulus29 by eliminating the ports 28 provided in the embodiment of FIG. 1 forfluid communication between the two. As a result, with the embodiment ofFIG 2, the gas flow rate to the melt through porous head 18 can bevaried as desired, without concern for the pressure needed to preventthe entry of the material of the melt into member 10.

I claim:

I. A method of treating a metallic melt contained within a vessel,comprising delivering from outside the melt downwardly through the meltto a location deep within the melt an additive reactive with the melt,isolating said additive from themelt until the additive reaches saiddeep location, simultaneously establish a first gas stream outside themelt, introducing said gas stream into the melt at said deep location ina finely subdivided state by passing said stream thereto through aporous refractory head, and stirring the dissolved unreacted additive bymeans of said finely subdivided stream. I

2. The method of claim 1 wherein the metallic melt is molten steel, theadditive is a deoxidant and the gas is a gas inert to the steel.

3. The method of claim 2 wherein the deoxidant is aluminum, and theinert gas is argon.

4. The method of claim 1 wherein the additive is delivered to the meltin the form of a rod.

5. The method of claim 4 wherein the metallic melt is molten steel, andthe additive is an alloying material.

6. The method of claim 4 including delivering the additive to the meltthrough a tubular member open at the bottom thereof to the melt andestablishing a second gas stream independent of the first gas streamwithin said tubular member.

7. The method of claim 6 including maintaining the pressure of thesecond gas stream at a value high enough to prevent the melt fromentering the tubular member at its open bottom.

2. The method of claim 1 wherein the metallic melt is molten steel, theadditive is a deoxidant and the gas is a gas inert to the steel.
 3. Themethod of claim 2 wherein the deoxidant is aluminum, and the inert gasis argon.
 4. The method of claim 1 wherein the additive is delivered tothe melt in the form of a rod.
 5. The method of claim 4 wherein themetallic melt is molten steel, and the additive is an alloying material.6. The method of claim 4 including delivering the additive to the meltthrough a tubular member open at the bottom thereof to the melt andestablishing a second gas stream independent of the first gas streamwithin said tubular member.
 7. The method of claim 6 includingmaintaining the pressure of the second gas stream at a value high enoughto prevent the melt from entering the tubular member at its open bottom.